I went to McDonald's last night after installing the Wallet apk. Actually, I went to two different McDonald's locations.
First time I went to order an actual meal. I tried to use the NFC chip with my Otterbox Defender case on. No dice. I thought I followed the instructions per the app, but the app didn't pull up or anything, so I paid by regular debit card.
I decided I was pretty damn determined to try this thing out, so I went to a different McDonald's to order a coffee (peppermint mocha, FYI). This time I had the Wallet app opened and I took the phone out of the Defender case and it worked flawlessly! Really quick. There were a bunch of people standing in line around me and they got really quiet all of a sudden when I paid for my coffee just by laying my phone on the credit card terminal.
So now that I knew that the app and NFC worked, I decided to put my phone back in the Defender case. I got up the courage to go back up to the register and asked for a bag of cookies (yes, a bag of cookies...) so I can start another transaction, this time with the phone in the case. The Wallet app and the reader were trying to communicate but the transaction just wouldn't go through. The cashier seemed a little peeved because she had to get a manager to void the transaction. So that kinda killed my showing-off...
So moral of the story: It doesn't work very well with the Otterbox Defender, which makes it kind of a hassle for me because I don't like to carry a naked phone or take the time to take it out of the case to pay for something.